Method for filling containers and installation therefor

ABSTRACT

A method for filling a plastic container ( 8 ) while it is still hot and deformable without damaging it, when the filling comprises a phase ( 17; 13 ) during which a noticeable difference in pressure between the container inside and the environment external to the filling installation occurs, at least during part of said phase, consisting in placing the container in a sealed chamber ( 9 ) isolating it from the external environment and modifying ( 18; 12 ) the pressure inside the chamber to reduce, even cancel, the difference in pressure between the container inside and outside. The invention is applicable to the filling of plastic containers, with aerated beverages and/or their filling after a vacuumizing phase of their internal volume, immediately after they have been made by blowing.

BACKGROUND OF THE INVENTION

The invention concerns improvements made at the time of fillingcontainers of plastic material, when such operation includes at leastone stage during which a significant difference in pressure occursbetween the interior of the container and the internal environment inthe filling installation, and when the operation is done when thecontainers are hot and have areas that are more or less malleable. Thisis the case when the filling phase of the container with any product ispreceded by placing them under depression (more or less significantvacuum) from the interior of the container, particularly while beingfilled with beer, or during overpressure when filling with a gaseousliquid, and when the containers are immediately filled after manufactureby blow molding or extrusion, blowing of a blank. It concerns aprocedure and installation for its embodiment.

The filling of a container with any product may sometimes be preceded byplacing the interior of the container under vacuum or pronounceddepression, for example to replace the air found in it by anothermedium, to avoid spoiling the product which will be finally packaged inthe container. For example, this is the case in the filling ofoxide-sensitive products such as beer, certain fruit juices and others:any trace of the oxidizing product must be removed, and in this case itmust be rendered inert, for example with nitrogen.

The filling of a container, such as a bottle, with gaseous liquidclassically consists of a phase of creating overpressure in the interiorof the bottle with a gas, typically carbon dioxide, followed by a phaseof filling with liquid, and a phase of depressurization to remove excessgas, while maintaining a certain gas pressure inside.

The pressure difference causes problems in plastic containers, whenfilling is attempted a few seconds after the containers came out of theblowing mold and are still hot, as is the case in the so-called in-linefilling installations.

With these containers, it is not possible to put them under depressionbefore filling, without causing deformation by collapse or crushing ofthe containers.

With the same type of containers, filling with gaseous liquids createsthe following problem: the overpressure phase of the containers beforefilling makes them burst or causes irreversible deformation.

The deformations or bursting affect the body of the containers, but onecan see deformations affecting more particularly the bottom of thecontainers (a phenomenon called “stress cracking” in professionallanguage).

These phenomena are due to the fact that the plastic container isobtained by blowing of a blank (preform, parison, intermediatecontainer), before bringing it to its blow temperature, thereforesoftened by heat. When the container comes out of the blowing mold, itstill has more or less hot zones, which are therefore more or lessmalleable. In general, these are the zones that are extruded the leastduring blowing, and which become cold more slowly for various reasons;and the bottom is one of the zones which are the least extruded.However, if, during the time the pressure difference is present, thetemperature exceeds the softening temperature even more, a deformationmay occur because of the mechanical force exercised on these zones byinternal pressure (overpressure or depression)

It also happens, although more rarely, that bursting or deformationsoccur when filling is done without creating depression or prioroverpressure with a gas, and the pressure at which the liquid isintroduced or, more generally, the pressure of the filling product ishigh.

Indeed, plastic containers and therefore their blanks are sized towithstand internal pressure values (overpressure or depression)necessary for the filling or the preservation of the products afterclosing, when the material is stabilized and therefore cooled.

This is why, until now, all filling attempts under the aforementionedconditions, with plastic containers which still have zones at atemperature higher than the softening temperature, and sized to withholdthe same conditions when the material is stabilized, have failed, andin-line filling was not applied at industrial scale.

A possible solution has been to oversize the containers in order tocompensate their formation by surplus material. This solution, however,is not realistic for several reasons, among which are: on the one hand,it is in contradiction with the current trend to make the containerslonger, for reasons of cost of materials; on the other hand, thecontainers contained are rather unaesthetic; in addition, paradoxically,the surplus of material makes the containers fragile when stabilized;finally, the surplus material necessary for filling, becomes uselesswhen the containers are cooled.

BRIEF SUMMARY OF THE INVENTION

The purpose of the invention is to remedy these shortcomings and allowfilling containers sized to withhold filling pressures when cold, butdeformable at least during part of the filling.

According to the invention, a procedure to prevent the irreversibledeformation or deterioration of a plastic container with at least onezone in which the temperature exceeds the softening temperature of thematerial, during a filling operation including a phase in which anotable pressure difference exists between the inside of the containerand the external environment in the filling installation, ischaracterized by the fact that, at least during part of such phase, aslong as it is not thermally stabilized and is still deformable, thecontainer is placed in an airtight enclosure which isolates it from theexternal environment, the pressure inside the enclosure is modified bycomparison to the external environment so as to reduce or even cancelthe pressure difference between the interior and the exterior of thecontainer.

Thus, by reducing or even canceling the pressure difference between theinterior and the exterior of the container, as long as the material isnot thermally stabilized, the risk of bursting or deformation iseliminated, and filling becomes possible while the container still hasmalleable zones.

According to another characteristic when the pressure difference betweenthe interior of the container and the external environment is obtainedby producing vacuum inside the container, the pressure inside theenclosure is modified, reducing it in order to bring it close or evenequal to the pressure inside the container.

Preferably, the reduction of the pressure inside the enclosure andinside the container are done simultaneously.

According to another characteristic, the filling product is a gaseousliquid, and the pressure modification is done by injecting a fluid underoverpressure into the enclosure, isolating the container from theexternal environment. In this case, the arrival of the filling liquidfavors the cooling of the container, which then stabilizes quickly.

According to another characteristic, the fluid is a gas in anembodiment, when the liquid is gaseous, the modification of the pressureis done with the help of the gas used in gasification (especially carbondioxide).

In this case, it is easy to achieve pressure balance between theinterior and the exterior of the container, by simultaneously modifyingthe pressure in the container and in the enclosure, in which case theproblems of bursting or deformation are totally eliminated.

BRIEF DESCRIPTION OF THE DRAWINGS

Other characteristics and advantages of the invention appear whenreading the description below, made in connection with the enclosedfigures, in which:

FIG. 1 illustrates schematically the various phases of filling withgasification, with resistant containers;

FIG. 2 illustrates schematically the principle of the invention appliedto filling with a gaseous liquid;

FIG. 3 illustrates schematically the principle of the invention appliedto the previous depression of the interior of a container;

FIG. 4 illustrates schematically the principle of the invention appliedto the previous depression of a container, followed by filling with agaseous liquid;

FIGS. 5 and 6 illustrate two possible embodiments of an installation forthe utilization of the invention for filling with a gaseous liquid;

FIG. 7 is a schematic view from above of an installation for embodiment;

FIGS. 8 and 9 are schematic views of variations of part of theinstallation for the embodiment of the invention;

FIG. 10 illustrates an advantageous embodiment of part of FIGS. of 8 and9.

DETAILED DESCRIPTION OF THE INVENTION

By referring to FIG. 1, a known cycle of filling of a container withgaseous liquid, such as a carbonated liquid, typically includes thefollowing phases.

1) “Phase 1”, during which the container, here a bottle 1, is introducedinto the filling machine and is positioned so that its next two is atthe level of the filling head 3. When bottle 1 is made of plastic,during the various phases, it is maintained under its next two, with thehelp of appropriate means, such as clamp 4, to avoid that, in subsequentphases, bottle 1 collapses under the pressure exercised by head 3.

2) A “phase 2”, in which bottle 1, and more precisely its neck 2, iscentered by comparison to the filling head the latter is affixed againstthe neck to ensure air tightness.

3) A “phase 3” of placing the interior of bottle 1 over pressure withthe help of an appropriate gas, typically carbon dioxide or a gas foundin natural state as a liquid. This phase of putting under internalpressure is carried out by injecting the gas through the conduit(s)going into the filling head 3. It is indicated schematically by arrow 5in the figures;

4) A “phase 4” of filling through the filling heads 3 (arrow 6 in thefigure);

5) A “phase 5” of evacuation of the excess gas in the container (arrow7) during this phase, the excess gas may be turned towards the tank fromwhich it was injected in phase 3;

6) A “phase 6” of releasing the filling head 3 and evacuation of bottle1, full, still held in place by clamp 4 under its neck 2.

Generally it is in phase 3 (putting under pressure) and/or phase 4(filling), that the bursting or deformation problems mentioned in thepreamble occur.

Of course, during filling without prior injection of gas, phases 3 and 5do not exist. It is during the filling phase (phase 4) that the problemscan occur, especially if the pressure and/or the filling rate are (is)too high.

FIG. 2 illustrates the principle of the procedure of the inventionapplied to filling plastic containers, such as bottles, with gaseousliquids, such as carbonated drinks.

The procedure may be summarized in three phases, illustrated by diagrams2-1, 2-2 and 2-3.

In FIG. 2-1:

After container 8, here a bottle, was placed in an air-tight enclosure9, and its neck 10 was put in air-tight communication with a fillinghead 11, gas is injected (arrow 12) inside container 8 through a conduitgoing into the head 11, and a fluid is injected (arrow 13) into theair-tight enclosure through a conduit, in order to exert counterpressure outside the container.

Preferably, the fluid used to exert counter pressure is a gas. A liquidcould also be used, but this would significantly complicate theembodiment of the invention: indeed, unless a non-wet liquid is used,the exterior of the containers would have to be dried after filling.

The moment the fluid is injected into the enclosure 9, as compared tothe moment the gas is injected into container 8, as well as the relativevalues of the pressures inside and outside the container are irrelevant:the essential point is that the difference in pressure must be at alltimes such as to avoid the bursting or deformation of the container.

However, preferably, in order to facilitate the embodiment of theprocedure, the injection of the counter pressure fluid and gas takeplace simultaneously.

As an alternative, it is possible to slightly delay the moment in whichthe increase in pressure begins in container 8 by comparison to the timethe increase in pressure begins in enclosure 9, starting first toincrease pressure in the container and then starting in enclosure 9,before the pressure in the container becomes too high.

Then comes the filling phase, through a conduit 14, in FIG. 2.2, duringwhich the counter pressure is preferably maintained. Indeed, it islikely that, in this stage, the container is not yet stabilized.

The next stage (FIG. 2.3) is degassing of the interior of container 8(arrow 15 in this figure) and a phase of relaxation of thecounterpressure (arrow 16 in the same figure) before the container comesout of the machine to be closed, or alternatively, closed before comingout, if the machine is a filling-closing machine.

In one embodiment, the counterpressure is released right before theinternal pressure is established, i.e., before filling or duringfilling. However, the process is more random and difficult to controlbecause if the container is not sufficiently stabilized, there can stillbe deformations and/or bursting.

In another embodiment, the release of the counterpressure starts afterdegassing begins, i.e., when it is certain that the constrains owed tothe pressure inside the container have totally disappeared. Thissolution offers a maximum of safety, but slows down significantly thetime of the cycle.

In an embodiment, the entire installation is under overpressure, toexert counterpressure outside the containers. However, this solution ishard to manage because it is necessary to provide means, such as traps,to allow the entry and exit of the containers without significantlyreducing overpressure inside the installation.

This is why, preferably, as illustrated in FIGS. 3 through 7, eachcontainer introduced in the filling machine is closed in an enclosurewhich isolates it from the rest of the environment of the machine. Whenthis enclose is closed, the gasification, counterpressure, filling,degassing and release of the counterpressure take place.

Thus, if the containers are introduced one by one, one group after theother, so as they go through the various phases in a staggered manner,each container is closed in a different enclosure than the preceding oneand the following one in the installation. On the contrary, if thecontainers are introduced by successive groups, then all the containersin a same group can be introduced simultaneously in the same enclosure,different than the preceding or following group. However, it is stillpossible to introduce all the containers of a same group simultaneouslyin different enclosures.

FIG. 3 illustrates the way the invention is applied to the prior puttingunder vacuum of a container 8, thus allowing to obtain, with plasticcontainers still malleable, what the prior state of the art did notallow.

After container 8 was locked in the air-tight enclosure 9, and its neck10 was put in communication with the filling head 11, a depression(arrow 17) is created inside the container and is accompanied (arrow 18)by a depression inside the enclosure, to avoid the collapse of container8.

Depressions in enclosure 9 and container 8 may have the same value, andtake place simultaneously. Then, a balance may be obtained between thepressure inside and outside the container.

Alternately, it is possible to slightly stagger the time the depressionbegins in the container, as compared to the time it begins in theenclosure, preferably by first creating vacuum in enclosure 9. Equally,the final values of the depressions in the enclosure and in thecontainer may not be equal. They must be adapted so that, finally, thecontainer does not undergo any undesired deformation.

After the depression in the container has produced its effect (forexample, preparation of an inert gas with nitrogen), an atmosphericpressure may be reestablished inside container 8 and enclosure 9. Forthis purpose, as illustrated in FIG. 3.2, both the interior of container8 and the interior of enclosure 9 are brought back to outside (arrows 19and 20, respectively).

Preferably, in order to avoid any deformation of container 8 in thisstage, it can be put back under atmospheric pressure before enclosure 9.

Then (FIG. 3.3), the container is filled (arrow 21). In this stage, itis no longer fundamental to keep it in enclosure 9 because the internalpressure in enclosure 9 is equivalent to the external pressure from thepreceding phase (FIG. 3.2), unless the purpose of filling was to gasifythe content, which will be explained with reference to FIG. 4.

The container may then be closed, and then removed.

As illustrated in FIG. 4, the invention presents the particularadvantage that the same installation can be used to combine the twomethods referred to in connection with FIGS. 2 and 3, respectively.

The same elements bear the same references.

After a container 8, here a bottle, was placed in the air-tightenclosure 9 (FIG. 4.1) a depression is created both inside the bottle(arrow 17) and in enclosure (arrow 18).

Then (FIG. 4.2), the interior of the bottle and that of the enclosureare placed under external atmospheric pressure (arrows 19 and 20), then(FIG. 4.3), the interior of the bottle and that of the enclosure can beput under pressure (arrows 12 and 13) before the bottle is filled (arrow14 in FIG. 4.4).

Then (FIG. 4.5), the pressure inside the enclosure and the bottle can bereleased (arrows 15 and 16), before the full bottle comes out of theenclosure (FIG. 4.6).

It is therefore conceivable that an installation for the implementationof the procedure according to the invention can be very simple to make:it suffices to have an air-tight enclosure with the appropriate conduitsin order to create vacuum in the enclosure and container and/or tocreate overpressure inside the enclosure and inside the container.

FIGS. 5 and 6 illustrate schematically two possible methods ofrealization of installations for the embodiment of the procedure underthe invention. More precisely, these figures show the parts of theinstallation used for filling with putting the container under vacuumand/or under internal overpressure.

These figures show in-line filling installations, in which thecontainers are continuously moved. Of course, the invention can apply toother types of installations.

The difference between FIGS. 5 and 6 is as follows:

in the method of embodiment in FIG. 5, the overpressure fluid of theenclosure associated to a container is different from that used tocreate overpressure inside the container. The enclosure can be put underoverpressure with compressed air, while the container is put underoverpressure with the gas used to gasify the filling produce (forexample, carbon dioxide in the case of carbonated drinks);

in the method of embodiment in FIG. 6, the gas which createsoverpressure in the container is also used to put the enclosure underoverpressure.

The latter solution has the advantage of creating isopressure betweenthe enclosure and the container. On the contrary, when the enclosure isopened, the quantity of gas remaining in the enclosure when degassing iscompleted is lost.

Consequently, it is not economical from the viewpoint of gasconsumption.

Due to the similarities existing between the two figures, the similar oridentical elements have the same references. On the other hand, in orderto simplify the understanding of these figures, whenever necessary,symbols were associated to the various conduits, showing the existenceor absence of flows of liquid and/or gas (arrows indicating theexistence and direction of a flow, or a line barring a conduit toindicate that it is or must be closed up, to prevent the passage ofliquid or gas).

The installations in FIGS. 5 and 6 are filling installations in whichthe containers pass continuously, i.e., each container, while beingcontinuously moved on a determined trajectory, is related to the meansto create vacuum and/or to create pressure, on the one hand, and fillingmeans, on the other hand.

FIGS. 5 and 6 show six containers (here, bottles) 220; . . . ; 225, eachassociated to a different enclosure, and therefore to different means tocreate vacuum and/or overpressure and filling.

Each enclosure consists of two different parts, respectively a top part230H; . . . ; 235H forming a lid and a bottom part 230B; . . . ; 235Bforming a receptacle to receive the corresponding container. Thedimensions of a receptacle 230B; . . . ; 235B are such that, when thelid 230H; . . . ; 235H is in place, the container is held in theenclosure, as explained below.

The top parts 230H; . . . ; 235H, as well as the bottom parts 230B; . .. ; 235B are affixed to the mobile structure 24 of the installation, sothat all the top parts 230H; . . . ; 235H follow the same trajectory,staggered over time, on the one hand and all bottom parts 230B; . . . ;235B follow the same trajectory, also staggered over time.

On the other hand, in the methods of embodiment illustrated in FIGS. 5and 6, each bottom part 23OB; . . . ; 235B can be removed from thecorresponding top part (lid) 230H; . . . ; 235H, especially in the facesin which the containers are put into place or taken out. For thispurpose, each bottom part is associated to means such as a guiding rod,respectively 250; . . . ; 255, for example sliding in a landing 260; . .. ; 265 built into the mobile structure 24.

Preferably, as illustrated by these FIGS. 5 and 6, the mobile structure24 causes a horizontal displacement of the top and bottom parts,respectively, and the means 250; . . . ; 255 260; . . . ; 265, cause avertical movement of the bottom parts 230B; . . . ; 235B, as compared tothe mobile structure when it moves in the direction of the arrow 27, andtherefore by comparison to the top parts 230H; . . . ; 235H.

For vertical movement, for example, as illustrated by these FIGS. 5 and6, there is a fixed cam 28 acting on a guide 290; . . . 295 respectivelyis provided, associated to each rod 250; . . . 255.

More precisely, the cam 28 is affixed on the frame, not represented, ofthe installation, so that, when the guide associated to a rod, andtherefore, to the corresponding bottom part (receptacle) meets the fixedcam, it follows the profile imposed by the shape of the cam, causing amovement that corresponds to the associated receptacle.

In the example illustrated by FIGS. 5 and 6, a first receptacle 230B isin bottom position. The corresponding container 220 has just beenloaded; the guide 290 is below the cam.

The second receptacle 231B, corresponding to the second container 221 ispartially raised.

The following three 232B; . . . ; 234B are totally raised and in contactwith their corresponding lid 232H; . . . ; 234H; consequently, theenclosures are closed, and the vacuum and/or application or pressure, aswell as filling, may take place.

Finally, the last receptacle 235B is descending, the correspondingbottle 225 being filled and liable to be released when the descent iscompleted.

Alternatively, it could be imagined that the bottom parts could beaffixed as compared to the mobile structure 24, with the top parts beingmobile in vertical movement as compared to this structure. This wouldsignificantly complicate the installation because, as illustrated byFIGS. 5 and 6, the top parts are associated to filling heads 300; . . .; 305 respectively, with conduits not only for filling, but also forcreating vacuum and/or pressure inside the enclosure and/or thecorresponding container, and means for anchoring the containers.

Preferably, as illustrated in FIG. 7, the installation can be of arotating type. In this case, the mobile structure 24 is a carouselturning around a rotation axis 31, the carousel bearing the enclosuresmore generally referenced under 23, with a top part (lid) 23H and abottom part (receptacle) 23B, and in this case, the cam 28 which leadsthe guides 29 is in the shape of a arc.

In a way that is generally known, the containers are introduced one byone into the installation (entrance showed by arrow 320 in FIG. 7); theyare grasped at the neck by the respective clamps 330; . . . ; 335associated to each filling head 300; . . . ; 305 (the clamps are shownin FIGS. 5 and 6). The clamps move vertically in order to place the lipof the containers against the filling head. The rising movement of eachclamp takes place, for example, when the container is going up. This issymbolized by an upwards arrow on clamp 331 associated to the container221.

After the filling and possible degassing of the associated container andenclosure, the corresponding clamp 335 descends again to release theneck of the container 225 from the filling head, before it comes out ofthe installation (the exit zone is shown by arrow 321 in FIG. 7).

In order to avoid overcharging FIGS. 5 and 6, the only conduitsillustrated are those which assure the internal overpressure of theenclosures and containers, and the filling of the latter. Equally, thereis no illustration of the connection between these conduits and thesources of liquid and gas, nor the sources themselves, because thespecialist will be able to reconstitute these connections from thedescription.

Each head 300; . . . ; 305 is crossed by a conduit 340; . . . ; 345 tocreate internal overpressure in the container (gasification) and by aconduit 350; . . . ; 355 for filling.

On the other hand, another conduit 360; . . . ; 365 is provided tocreate internal overpressure in the enclosure.

In FIG. 5, the conduit 360; . . . ; 365 open in the corresponding bottompart 230B ; . . . ; 235B, alternatively, as illustrated in FIG. 6, theyopen in the top part 230H; . . . ; 245H.

In FIG. 5, the conduit 140; . . . ; 345 for the gasification of thecontainers are independent from conduit 360; . . . ; 365 which createinternal overpressure in the enclosures. Thus, it is possible to placeeach enclosure under overpressure with a fluid other than the gas forgasification of the filling product. As an example, it is possible touse compressed air in order to create overpressure inside the enclosure.

In FIG. 6, each conduit 340; . . . ; 345 for the gasification of acontainer is associated (by a bypass) to the corresponding conduit 360;. . . ; 365 for creating overpressure in the enclosure. Thus, the gasfor the gasification of the container can also be used to createoverpressure in the enclosure.

Overpressure and filling operations are conducted after the enclosure isclosed, as described concerning FIG. 3. In the example in FIGS. 5 and 6,the container 222 and the corresponding enclosure 232H, 232B are aboutto be placed under overpressure; the container 223 is about to befilled, the pressure in this container and in the enclosure aremaintained (as shown by a bar across conduit 363 which creates pressurein the enclosure) container 224 is full, and pressure is released bothin the container and in the enclosure; finally, the bottom part 235B ofthe enclosure associated to the container 225, full, is about to descendto allow the container to exit.

FIG. 8 shows the diagram of principle of a perfected top part 23H, whichcan be adapted to the method of embodiment in FIG. 5 while also allowingthe depression in the container and enclosure.

In addition to the conduits, more generally designated by 34, for thegasification of the container 22 through the filling head 30, 36 forcreating overpressure in the enclosure, and 35 for filling through thehead 30, there are two conduits, respectively 37 for creating vacuum inthe enclosure and 38 for creating vacuum in container 22 through thehead 30. These two latter conduits are either connected between them asillustrated in FIG. 8, which allows connecting them to a common vacuumpump (not shown), or are not connected between them, but they areconnected to separate pumps.

On the other hand, the conduit 34 for gasification of the content and 36for creating overpressure in the enclosure are separated, allowing, forexample, to place the enclosure under overpressure using compressed air.

In FIG. 9, which is a diagram of principle of a perfected top part 23Hadaptable for the method of embodiment in FIG. 6, while also allowing tocreate depression in the enclosure and in the container 22, one findsthe same conduits as in FIG. 8, but the conduits, respectively, 34 forgasification of the content and 36 to create overpressure in theenclosure, are connected between them, allowing to create overpressurein the enclosure with the gasification gas.

A problem presented by the methods of embodiment in FIGS. 5, 6, 8 and 9is that two conduits 34, 35 or three conduits 34, 35, 36 cross thefilling head 30, which somewhat complicates its structure.

This is why, in a method of embodiment illustrated in FIG. 10, theconduits are connected to a valve 39 with mechanical control 40,electric or other type of control.

An intermediary conduit 41 is connected to the head 30 and establishescommunication between this valve and the interior of the container 22.By operating the control 40, communication is established between theinterior of the container 22 either with the vacuum conduit 38 (when itexists) or with the gasification conduit 34 (when it exists), or withthe filling conduit 35.

The invention allows filling containers which are still hot andtherefore deformable, without causing them irreversible deformations,because of the limitation of the difference in pressure it allowsbetween the interior and exterior of the containers. In addition, it hasbeen found that the filling liquid contributes to cool the bottom of thecontainers before external pressure is brought back to the ambientlevel. Consequently, the bottoms are stabilized when the exteriorpressure is released.

Of course, as it arises from the above, the invention is not limited tothe methods of embodiment and application which were more particularlyconsidered: on the contrary, it covers all variations.

What is claimed is:
 1. Method to prevent the deformation or theirreversible deterioration of a plastic container (8; 22; 220; . . .225), having at least one zone where the temperature exceeds thetemperature needed to soften the material, when a filling operation thathas a phase during which a noticeable pressure difference occurs betweenthe internal part of the container and the external environment at thefilling installation, characterized, at least, during a part of thementioned phase, which is not thermally balanced and is stilldeformable, being the container placed inside a tight chamber (9; 23B,23H; 230B, 230H; . . . ; 235B, 235H) and isolated from the externalenvironment; the internal pressure of the chamber is modified inrelation to the external environment, in order to reduce, or even tocancel, the difference in pressure between the internal and externalparts of the container.
 2. A method of claim 1, characterized by thedifference of pressure between the internal part of the container andthe external environment, being obtained by creating a vacuum (17) inthe container; the pressure in the internal part of the chamber ismodified by reduction (18) in order to be closer, or even reach, thepressure of the internal part of the container.
 3. A method of claim 2,characterized by the fact that the reduction of the pressure inside thechamber is started before the reduction inside the container.
 4. Amethod of claim 1, characterized by the filling being carried out with aproduct, such as a liquid, gasified, and comprising, consequently, aprevious phase of overpressure (12) inside the container with the gasserving for the gasification; the modification of the pressure insidethe chamber being carried out by means of injecting (13) a fluid underoverpressure in the chamber.
 5. A method of claim 4, characterized bythe fluid which is a gas.
 6. A. A method of claim 5, characterized bythe fact that the gas injected in the chamber is the same as the gasused for gasification inside the container.
 7. A method of claim 5,characterized by the fact that the gas injected in the container isdifferent from the gas injected in the chamber.
 8. A method of claim 7,characterized by the fact that the gas is compressed air.
 9. A method ofclaim 4, characterized by the fact that the modification in chamberpressure to be put under overpressure is started after the modificationin the container.
 10. A method of claim 1, characterized by the factthat modification of the pressure inside the chamber and themodification of the pressure inside the container take placesimultaneously.
 11. Application of a method of claim 1 for filling aplastic container obtained by heat, then blowing, alternativelyextending/blowing, pre-shaping, immediately after blowing andalternatively extending/blowing.
 12. Installation for the operation ofthe method of claim 1, characterized by the fact that it has, at least,one tight chamber (9; 23B; 23H; 230B, 230H; . . . ; 235B, 235H) toreceive, at least said deformabled plastic container (8; 22; 220; . . .225), a means to put the internal part of the container in communicationwith a filling conduit (14; 21; 35; 350; . . . 355), and a means toprevent irreversible deformation or deterioration of said plasticcontainer while the temperature of said plastic container exceeds thetemperature needed to soften the material of the container whichincludes a means to modify the pressure in the internal part of thechamber and in the internal part of the container.
 13. Installation ofclaim 12, characterized by the fact that the means which are to modifythe pressure in the internal part of the chamber consist of a conduit(37) that puts the chamber in communication with the means to reduce(18) the pressure in the internal part of the chamber, and the means tomodify the pressure in the container consists of a conduit (38) puttingthe container in communication with the means to reduce (17) thepressure in the internal part of the container.
 14. Installation ofclaim 13, characterized by conduits (37; 38) associated with a chamberare connected between themselves, and a single medium, such as a vacuumpump, is used to reduce the pressure in the chamber and in thecontainer.
 15. Installation of claim 14, characterized by conduits (37;38) which together with a chamber are connected to separate media, suchas a vacuum pump, used to reduce the pressure in the chamber and in thecontainer.
 16. Installation of claim 12, characterized by the fact thatthe means to modify the pressure in a chamber consist of a conduit (36,360, . . . ; 365), putting the chamber in communication with the meansto increase (13) the internal pressure and the means to modify thepressure in the container consist of a conduit (34, 340; . . . , 345)putting the container in communication with the means to increase (12)the internal pressure.
 17. Installation of claim 16, characterized bythe fact that the conduits (36; 360; . . . ; 365; 34; 340; . . . ; 345)connected to a chamber are connected between themselves and to a singlesource of fluid, in order to increase the pressure in the chamber and inthe container.
 18. Installation of claim 17, characterized by the factthat once the filling product is gasified, the only source of fluid isthe source of production of the gas of gasification.
 19. Installation ofclaim 16, characterized by the fact that the conduits (36; 360; . . . ;365; 34; 340; . . . ; 345) connected to the same chamber are connectedto different sources of fluid to increase the pressure in the chamberand in the container.
 20. Installation of claim 12, characterized by thefact that each chamber comprises two separable parts, a high part (23H;230H; . . . ; 235H) forming a cover connected to the filling head (30;300; . . . ; 305) and a short part (23B; 230B; . . . ; 235B) forming areceptacle to receive the container (22; 220; . . . ; 225). 21.Installation of claim 20, characterized by the fact that it comprisesthe means (28; 250; . . . ; 255; 260; . . . 265; 290; . . . ; 295) toget close to or distant from the corresponding receptacle. 22.Installation of claim 21, characterized by the fact that it comprisesthe means (24) to support the high parts and the short parts, allowing ahigh part to get close in relation to the corresponding short part andto move the said parts along a determined route (27).
 23. Installationof claim 21, characterized by the fact that the support means (24) andthe movement of a chamber are a carrousel turning around an axis (31Y,and the means to get the high and short parts close consist of a cam(28), fixed in relation to the installation, the said cam cooperatingwith at least a trail (290; . . . ; 295) associated with a shaft ofsupport and guidance for one of the parts of the chamber. 24.Installation of claim 23, characterized by the fact that the shaftsupports the short part (230B; . . . ; 235B) of the chamber.